Field of the Invention
Embodiments of the invention relate to power conversion, in particular to resonant power conversion.
Description of the Related Art
Resonant converters provide many advantages over other types of power converters, such as low noise, low component stress, low component count, and predictable conduction-dominated losses. Some resonant converters may employ four quadrant (4 Q) bidirectional switches within an AC switching stage in order to handle both the positive and negative voltages required. A fully controlled 4 Q bidirectional switch may be implemented, for example, using two source-connected high-voltage metal-oxide-semiconductor field-effect transistors (MOSFETS).
In some resonant converter topologies employing 4 Q switches, one or more of the MOSFETs within the 4 Q switches may be statically held “on” during the positive half-cycle of the AC waveform while the remaining MOSFETS are actively switched, and other MOSFETs may be statically held “on” during the negative half-cycle of the AC waveform while the remaining MOSFETS are actively switched. Although such an operating technique results in lower gate drive losses than if all of the MOSFETS are actively switched, in resonant converters having high resonant frequencies all of the MOSFETs in the 4 Q switches must still be high-performance, high-frequency switching devices that result in greater switching losses and are more costly than lower-performance, lower-frequency switching devices.
Therefore, there is a need in the art for a method and apparatus for efficiently converting a DC voltage to an AC voltage using a resonant converter.